Etching process

ABSTRACT

A method for etching a pattern in a material in precise target areas comprising depositing selectively onto the material droplets of a substance for dissolving or reacting chemically with the material. Droplets may be deposited from a print head of the type having a nozzle from which the material may be ejected as a series of droplets, such as an ink jet print head. In a preferred application, a series of ridges can be etched from an organic insulator layer overlying a photoemissive organic polymer. A conductive layer is then deposited and the ridges of organic insulator are dissolved by solvent washing to provide an array of conductive stripes which can be used as a cathode for an electroluminescent display device. In combination, both anode and cathode can be fabricated for a display device without the need for photolithography, which is particularly advantageous for the fabrication of large area display devices.

BACKGROUND

The present invention relates to etching of materials.

In many modern industrial processes it is necessary to etch intricateand accurately defined patterns in a material. The etching may beconfined to within the material or the etching process may be continueduntil the material is etched through, thereby to expose an underlyingmaterial. In many industrial applications such as, for example, thefabrication of electronic, optical or optoelectronic devices, theetching steps form a very critical phase of device fabrication, as theetching process usually dictates the accuracy to which the devices areultimately manufactured.

The use of etch masks, such as photo masks or shadow masks, is wellknown in such fabrication techniques. Hence, these processes will not bedescribed in detail in the context of the present invention. However, inrecent years, new forms of devices have been proposed for which suchconventional etching techniques present severe process concerns.Furthermore, the etching of relatively long but extremely narrow lineshas, for a long period of time, presented severe fabricationdifficulties as it is very difficult to produce mechanically robust etchmasks which will provide the required definition in the finishedproduct.

Other concerns are also known to exist with known etching techniques.For example, in certain processes where it is required to etch through alayer of material to expose a pattern of an underlying material, such asa substrate, the surface of the substrate usually exhibits a degree ofuneveness which can be regarded as a series of peaks and troughs.Therefore, to etch through the material to leave an exposed pattern ofthe substrate without any residue of the material being etched usuallyrequires the etch process to be continued after initial exposure of thepeaks on the surface of the substrate. The substrate itself is thereforealso etched in the etching process. In many cases this may beundesirable as the substrate surface may have been provided with a verythin coating and therefore the etch process must necessarily be verycarefully controlled to ensure that over etching does not occur.Additionally, extensive research is now taking place into the use ofsemiconductor organic materials in electronic devices, for exampledisplay devices, incorporating electroluminescent organic polymer lightemitting diodes or integrated circuits incorporating organic polymertransistors. Conventional known etching processes present even greaterconcerns for the fabrication of such devices, as will be outlined below.

Electroluminescent displays represent a novel approach for fabricatinghigh quality, multicolour displays. In an electroluminescent display asoluble polymer is deposited onto a solid substrate, such as forexample, glass, plastics or silicon. Inkjet printing techniques havebeen proposed to deposit the soluble polymers not only because of therelatively low cost of such techniques but also because of the abilityto use inkjet technology for large area processing and, therefore, thefabrication of relatively large area displays. For a multicolourelectroluminescent display a number of soluble organic polymers may eachbe deposited as an array of dots of the polymers to provide the red,green and blue emissive layers for the display. The use of an inkjettechnique makes this deposition of different polymers possible withoutdeterioration of the polymer materials caused by the patterningprocesses.

Generally, two kinds of driving scheme can be used to address the pixelsof the display. One is a passive matrix and the other is an activematrix scheme. The active matrix has patterned anode pixels, each withthin film driving transistors (usually two per pixel as the organicpolymers are current driven devices) and a common cathode. In order tofabricate the patterned anode pixels and the thin film transistors(TFT's), conventional photolitographic technology is generally used.This process is carried out before the deposition of the organic layersso it does not affect the performance of the organic polymer materials.Fine patterning to fabricate the cathode is not required as the cathodemay be a conductive layer common to all of the pixels. Hence, the commoncathode can be fabricated over the organic layers using an evaporationtechnique, with the use of a metal shadow mask to define the edge frameof the cathode.

The passive matrix driving scheme uses patterned anodes and cathodesarranged as mutually perpendicular row and column electrodes on eitherside of the organic polymer emissive layers. In terms of the depositionof a cathode, the active matrix scheme is easier to fabricate, but theactive matrix scheme still costs more to produce than the passive matrixscheme due to the formation of the TFT's for each pixel. Hence, thepreferred way of driving such a display is to use a passive matrixaddressing scheme. However, there are significant technical difficultiesassociated with the patterning of the anode and, in particular, thecathode for such displays.

The anode may be fabricated directly onto the substrate prior to thedeposition of any soluble organic polymer layer. The anode is usuallyfabricated from indium tin oxide (ITO), as this material is conductiveand relatively transparent. The ITO layer is formed as a continuouslayer on the substrate and is then patterned using a photolithographicprocess to provide the anode array. However, the photolithographicprocess requires the use of a photo mask. Whilst such photo masks arecommonly used to fabricate the anode array, their use becomesincreasingly difficult as the size of the display area increases becauseproblems are encountered in maintaining the required accuracy ofdefinition throughout all areas of the mask. For use with large areaelectroluminescent displays, the use of such photo masks becomesprohibitively expensive which negates the potential cost benefitsarising from the use of the relatively inexpensive organic polymermaterials.

With regard to the cathode, the patterning of the cathode for an organicpolymer display gives rise to significant difficulties. The cathode mustnecessarily overlie a soluble organic polymer layer. The traditionalphotolithographic techniques cannot be used for the patterning of thecathode as the etchants used severely damage or degrade the underlyingorganic materials. Other techniques have, therefore, been proposed forcathode patterning, such as the use of a stainless steel shadow mask,but such masks lack the required resolution in the fabricated array.Furthermore, the use of pre-patterned mushroom shaped photoresistdividers has also been proposed but such dividers are costly to produceand, in view of their fabrication process, are not suitable for largearea patterning.

It has also been proposed to pattern a shadow mask through the use ofinkjet printing of inert polymers followed by a lift off step using anadhesive tape. However, such a process suffers from poor resolution andusually gives rise to an unacceptably high density of defects in theachieved cathode array.

SUMMARY

It can be seen, therefore, that there is a need to be able to reliablyfabricate well defined patterns in a material, including relatively longbut extremely thin narrow lines, by a process which does not rely on theuse of a photo mask or a shadow mask. Furthermore, there is also a needto be able to readily select the etching substances so that anunderlying layer to a layer to be etched can act readily as an etch stoplayer for the selected etch substance. This would assist significantlythe etching process as the etch step could be continued to ensure gooddefinition in the etch pattern without concern for damaging orcontaminating the underlying layer. This is particularly so for thefabrication of organic polymer devices such as organic polymer displays,where such a process could then be adopted to enable the anode and thecathode for the display to be fabricated by a cost effective solution,even for large area displays, without the contamination concerns arisingfrom the use of known etch processes.

According to a first aspect of the present invention there is provided amethod of etching a material in precise target areas comprisingdepositing selectively onto the material a substance for dissolving orreacting chemically with the material.

By depositing an etchant in accordance with the present invention it ispossible to etch precise target areas without using a mask, thusavoiding the difficulties associated with the use of masks as discussedabove. Very precise etching of localised target areas is possible inaccordance with the present invention.

Preferably, the substance is deposited from a print head of the typehaving a nozzle from which the material may be ejected as a series ofdroplets. Advantageously, the method comprises etching through thematerial to expose an area of an underlying material.

Most advantageously, the underlying material comprises an etch stoplayer for the substance.

In a preferred arrangement the method comprises etching an array ofholes in the material thereby to provide an array of exposed areas ofthe underlying material.

In an alternative arrangement the method comprises exposing an area ofthe underlying material in the form of an elongate strip.

Advantageously, the method comprises exposing a plurality of elongatestrips of the underlying material.

Preferably, the elongate strips are substantially parallel so as toprovide an array of substantially parallel elongate strips of exposedareas of the underlying material spaced by elongate strips of thematerial.

Most preferably, the or each elongate strip has a width less than thediameter of a droplet of the substance upon deposition onto thematerial.

In a preferred arrangement, the material includes boundary portionsdefining the or each elongate strip and wherein further droplets of thesubstance are deposited onto one of the boundary portions, thereby tocause the said one of the boundary portions to migrate towards the otherboundary portion and reduce the width of the elongate strip.

Advantageously, the method further comprises etching the exposed area orareas of the underlying material using a dry or a wet etch process.

Preferably, the exposed area or areas of the underlying material areetched by depositing a further substance from a print head of the typewherein the further substance is deposited from a nozzle in the form ofdroplets.

Most preferably, a further material is deposited into contact with theexposed area or areas of the underlying material.

The further material may be deposited as a layer overlying the materialand extending into contact with the exposed area or areas of theunderlying material.

Advantageously, the further material is selectively deposited byevaporation or sputtering.

In an alternative arrangement the further material is selectivelydeposited in liquid form on to the exposed area or areas of theunderlying material from a print head of the type in which the furthermaterial is deposited in the form of droplets from a nozzle.

Most advantageously, the exposed area or areas of underlying materialhas a wettability for the further material which is greater than thewettability of the material for the further material so as to provideself alignment of the further material on the exposed area or areas ofunderlying material.

In a first preferred arrangement the material is removed to provide anarea or areas of the further material.

Advantageously, the material comprises an organic material, thesubstance comprises a solvent for the organic material and the furthermaterial comprises a layer of conductive material.

Preferably, the conductive material comprises a material which has awork function of less than about 4.0 electron volts.

The underlying material may comprise polyfluorene or copolymer offluorene in combination with a conjugated molecule group and the organicmaterial may comprise polyvinyl phenol, polyvinyl alcohol orpolymethylmethacrylate (PMMA).

Advantageously, the organic material may comprise a conjugated moleculeor conjugated polymer.

Preferably, the solvent comprises at least one of methanol, ethanol,dimethylimadizolinidine, butanol, 1-propanol or 2-propanol.

Most preferably, the underlying material is supported on a substratewhich may comprise rigid glass, plastics or silicon or, alternatively, aweb of spoolable plastics material.

By using the above method an electrode array, such as a cathode array,may be fabricated for a display device.

In an alternative arrangement the material comprises an organicmaterial, the further material comprises a further organic material andthe substance comprises a solvent for the organic material.

Preferably, the organic material comprises a non-polar organic materialand the further organic material comprises a polar organic material oran organic material suspended in a polar solvent so as to provide selfalignment of the further organic material on the exposed area or areasof the underlying material when deposited from the print head.

Advantageously, the further organic material comprises a conductiveorganic material.

Preferably, the conductive organic material comprises Poly-3,4-ethylenedioxythiophene.

In a preferred arrangement the method comprises dry etching using aplasma of fluorinated carbon prior to the deposition of the furthermaterial which advantageously may be preceded by dry etching using aplasma of oxygen.

Preferably, the organic material, which may comprise a non polarpolymer, is removed with a solvent, which may comprise a hydrocarbonicsolvent.

In a most preferred arrangement, the underlying material comprises asubstrate, which may comprise rigid glass, plastics or silicon or,alternatively, a web of a spoolable plastics material.

In accordance with the above alternative arrangement, an electrodearray, such as an anode array, may be fabricated for a display device.

Advantageously, the method may further comprise providing an overlayerof polyvinyl phenol, polyvinyl alcohol or polymethylmethacrylate (PMMA).

The overlayer may also comprise a conjugated molecule or a conjugatedpolymer.

Alternatively, the substance may react chemically with the material toform a further substance for removal by washing.

Preferably, the material comprises a non-transparent material, thesubstance comprises an alkyl solution or an acid solution and thematerial comprises a metal soluble in the alkyl solution or the acidsolution. In the above manner, it is possible to fabricate an etch maskor a shadow mask.

According to a second aspect of the invention there is provided adisplay device comprising an electrode fabricated in accordance with theabove first preferred arrangement and/or an electrode fabricated inaccordance with the above alternative arrangement.

The display device may advantageously comprise an organic polymeremissive layer including polyfluorene or copolymer of fluorene incombination with a conjugated molecule group.

In a third alternative arrangement, the material may comprise afluorinated polymer layer and the substance comprises a fluorinatedorganic solvent for dissolving the fluorinated polymer layer thereby toprovide a dewetting bank structure in the fluorinated polymer layer.

According to an alternative aspect of the invention, there is provided adewetting bank structure fabricated by a method in accordance with thethird alternative arrangement.

In a further aspect of the present invention, the further material maycomprise DNA or a protein.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described, by way offurther example only and with reference to the accompanying drawings inwhich:—

FIG. 1 is a diagrammatic illustration of an organic polymer displaydevice.

FIG. 2 is a diagrammatic illustration of a known photolithographicpatterning technique.

FIG. 3 is a schematic illustration showing the use of a metal shadowmask for cathode patterning.

FIG. 4 is a diagrammatic illustration of prepatterned mushroom shapedividers for cathode patterning.

FIG. 5 is a diagrammatic illustration a polymer mask fabricated byinkjet deposition.

FIGS. 6A to 6F show diagrammatically the process of inkjet etching of anorganic polymer layer.

FIGS. 7A and 7B show diagrammatically one of the benefits arising frometching with a substance for which an underlying layer is able to act asan etch stop layer for the substance.

FIG. 8 illustrates plots of layer thickness achieved during inkjetetching.

FIGS. 9A and 9B illustrate how the present invention can be employed tofabricate relatively long but very narrow etched lines in a material.

FIGS. 10 to 10H illustrate diagrammatically an embodiment of the presentinvention for the fabrication of a cathode for the display device shownin FIG. 1.

FIGS. 11A to 11F illustrate diagrammatically a further embodiment of thepresent invention for the fabrication of an anode for the display deviceshown in FIG. 1;

FIG. 12 is a schematic view of a mobile personal computer incorporatinga display device having a driver according to the present invention;

FIG. 13 is a schematic view of a mobile telephone incorporating adisplay device having a driver according to the present invention,

FIG. 14 is a schematic view of a digital camera incorporating a displaydevice having a driver according to the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Various aspects of the present invention will now be described withreference to the fabrication of an anode and a cathode for organicpolymer electroluminescent and photoluminescent display devices by theuse of inkjet etching.

Referring to FIG. 1, an organic polymer display device comprises asubstrate 2, such as glass or plastics material, supporting an anode 4in the form of an array of horizontal row electrodes of conductivematerial, such as ITO, ZnO2, or a thin metal film, which issemi-transparent. An organic polymer layer 6 is provided to overly theanode 4. The layer 6 might typically comprise small molecules of Alq3 ora conjugated polymer mix of F8/F8BT/TFB, where F8 is[poly(9,9-dioctylfluorene)], F8BT is[poly(9,9-dioctylfluorene-co-2,1,3-benzothiadizole)] and TFB is[poly(9,9-dioctylfluorene-co-N-(4-butylphenyl) diphenylamine)]. Theseconjugated polymers are derivatives of polyfluorene, and they aresoluble in organic solvents, such as chloroform, toluene and xylene.Spin coating is used to make a monochrome display, and inkjet depositiontechniques have been developed to deposit different polymers formulti-colour display. A cathode 8, in the form of an array of verticalcolumn electrodes of a conductive material, is provided on the polymerlayer 6. In order to assist electron injection into the polymermaterials, low work function elements typically having a work functionof less than about 4.0 electron volts, such as, Ca, Li, Mg, Al, Ti, andrare-earth elements are used for the cathode electrodes. These elementsare chemically unstable in general.

In a typical display device the anode 4 may be fabricated by depositinga layer of ITO onto the substrate 2 and then etching the ITO layer usinga conventional photolithographic process. Such a process can achievevery high resolution and can be readily used because the anode 4 isformed directly on the substrate, which is usually glass, plastics orsilicon. However, photolithographic techniques are relatively complexand are time consuming and costly to implement. Additionally, thiscomplexity is enhanced with increase in the size of display as thephotolithographic mask becomes extremely difficult to fabricate to therequired definition over all areas of the mask. Hence, such techniquesare not ideally suited to even the fabrication of the anode in anorganic polymer display as the lower cost benefits of the organicpolymer materials, and in particular in the production of larger sizedisplays, cannot be fully realised.

Photolithographic patterning of a layer, such as the patterned layer 10illustrated schematically in FIG. 2, which typically could comprise thecathode shown in FIG. 1, can be achieved in conventional LCD or LEDdisplays by using a photoresist in combination with either dry or wetetching to selectively remove the unwanted areas 12 to provide therequired pattern in the patterned layer of the photoresist 10.Alternatively, the photoresist layer may be used in combination with anevaporation or “lift-off” technique to achieve the required pattern.Such techniques are well known in the art and will not, therefore, bedescribed further in the context of the present invention. However, ascan be seen from FIG. 1, in an organic polymer electroluminescentdisplay the cathode 8 overlies and is in contact with the organicpolymer layer 6. Hence, for the fabrication of the cathode 8, verysevere difficulties and drawbacks are encountered if a photolithographictechnique is utilised.

Because the layer 6 is in an organic material, it will react with thechemicals used in the photolithographic process, such as the photoresistsolution, the developer, and the stripper used to strip the photoresistlayer after patterning of the layer. For example, the organic materialof the layer 6 may be dissolved and/or it may be doped by thephotoresist materials. The doping can take many forms but typically thiscan give rise to quenching or site trapping within the organic material.Furthermore, UV light, which is used for the exposure of photoresist,can give rise to photo-oxidation or bonding defects in the organiclayers. These not insignificant difficulties arising from the reactionof the organic polymer materials to the conventional photolithographicprocess are far more serious than the actual cost burden of the processitself, because the actual performance quality of the organic materialsis seriously degraded by the use of the process; i.e. a lowerperformance display is created but with high fabrication costs..

The use of metal shadow masks has also been proposed for cathodepatterning. As can be seen from FIG. 3, this process involves the use ofan apertured metal mask 14, usually of stainless steel. The cathodematerial is deposited by evaporation deposition but the mask 14 isspaced slightly from the organic layer so as to prevent the metal maskfrom contaminating the organic layer and from creating defects in theorganic layer. As the evaporated material passes through the apertures18 in the mask its deposition angle can change in direction, depositingmaterial over a wider area than that defined in the mask and giving poorresolution for the deposited cathode. Furthermore, the mask mustnecessarily be a negative image of the actual required cathode patternso the mask comprises only relatively thin strips of metal(corresponding to the spacing between the elements in the cathode array)arranged between relatively large apertures. For this reason the mask isnot mechanically robust and cannot be used to fabricate cathodes forlarge area displays. If the mask is made more robust by providing widerstrips of metal, there is a corresponding increase in the spacingbetween adjacent electrodes of the cathode, which reduces the emissivearea and the resolution of the display. Additionally, a paralleldeposition beam is necessary over the entire area of the display. Aswill be appreciated, as the display area is increased, it then becomesnecessary to increase the distance between the source of cathodematerial and the target substrate in order to ensure that a parallelmaterial beam is provided throughout the relatively large depositionarea. The deposition chamber becomes, therefore, large in size andfurthermore, most of the evaporated material deposits on the walls ofthe chamber and not on the target substrate. Both of these factorsincrease processing costs and, hence, the cost of the final displaydevice. Additionally, to enable the shadow mask to be reused, materialwhich is deposited on the shadow mask must be removed to maintain therequired definition of the apertures 18 in the mask. Cleaning of theshadow mask can also be problematical, giving rise to further increasedproduction costs for the display device.

Pre-patterned mushroom shape dividers 20, as shown in FIG. 4, have alsobeen proposed for cathode patterning. The mushroom shape dividers areformed on the substrate, with the subsequent deposition of the organicpolymer material 6 and the cathode 8. With these mushroom-shapeddividers, it is possible to form cathode columns, which are electricallyisolated from each other, without the use of a metal shadow mask.However, the mushroom shape dividers 20 are usually fabricated by acombination of a photolithographic process and an isotropic etchingprocess, which requires a mask and is a relatively lengthy and,therefore, expensive process. Furthermore, in view of the angle of thedeposition beam required to deposit the cathode material, deposition ofthe material onto side surfaces 22 of the mushroom shape dividers 20 mayoccur due to the obliquely incident deposition beam, giving shortcircuits between the cathode columns. These difficulties increase withthe size of the display area because the evaporating deposition processfor a large area requires a more oblique deposition beam than for asmall area. It follows, therefore, that such dividers are not suitablefor large area patterning of cathodes.

The use of an inkjet printed shadow mask of an inert polymer has alsobeen proposed for the fabrication of a patterned cathode on the emissiveorganic polymer layer. The polymer mask 24, a portion of which is asshown in FIG. 5, is printed as a series of lines onto the organicpolymer layer, the spacing between the inkjet printed lines determiningthe width of the electrodes in the subsequently deposited cathode. Theinert polymer mask 24 in the bump areas shown in FIG. 5 is lifted offusing a weak adhesive tape. However, in such an arrangement, the linewidth of the inkjet deposited mask is relatively large, typicallygreater than 100 microns, which reduces the emissive areas in the finaldisplay. This is highly undesirable, especially in high definitiondisplays. This line width arises because it is difficult to draw narrowlines with an inkjet patterning technique due to spreading of depositedsolution on the surface. The spreading of the solution of the inertpolymer also results in thin thickness in the deposited material, whichmakes it difficult to apply the conventional lift-off technique.Additionally, the process also gives rise to a relatively high densityof defects, again affecting image resolution.

The above concerns exist not only with organic polymer displays but alsowith the fabrication of other electronic devices, but in particularthose incorporating organic semiconductor materials. Furthermore, asstated previously, the patterning of relatively long but extremelynarrow lines has always proved problematical because the etch maskscannot be provided with sufficient mechanical robustness to accuratelydefine such lines. The present invention seeks to provide a solution tothese concerns with the known techniques by depositing an etchant ontothe material to be etched in the form of droplets. If the deposition ofthe droplets can be adequately controlled, and the etchant is chosen soas to dissolve or react chemically with the material to be etched, veryfine and accurately defined patterns may be etched in or through thematerial without the requirement of a photolithographic or shadow mask.

It has been realised with the present invention that such accuratedeposition of the etchant can conveniently be achieved through the useof a print head of the type having a nozzle from which the material maybe ejected as a series of droplets. A readily available print head ofthis type is an inkjet print head and the present invention will besubsequently described with reference to such a print head. However, itis to be realised that other mechanisms can also be used to carry outthe method of the present invention such as the use of a very fine, forexample a micro-pipette, moved under computer control over the surfaceof the material to be etched. Typically, the nozzle used to carry outthe method of the present invention will have an ejection orifice ofless than about 100 microns diameter.

Additionally, the present invention is also described below withreference to the use of a solvent as the etchant material. However, itshould also be appreciated that the etchant may equally comprise asubstance which reacts chemically with the material to be etched toprovide a further material which can, for example, be removed bywashing.

Referring now to FIGS. 6A to 6F, the present invention will be describedwith reference to the principle of inkjet etching to pattern holes orlines in an organic layer. This principle of etching, in particular bythe use of an inkjet print head, has been found to be particularlyadvantageous because, as will become apparent from the followingdescription, the use of such inkjet print heads for etching enables bothan anode and a cathode for a display to be fabricated without the use ofphotolithography or shadow masks. For organic polymer displays inparticular, this becomes increasingly important with increase in displayarea as the difficulties, and hence the costs of using known processesutilising photo or shadow masks, increases significantly.

FIGS. 6A to 6F illustrate the principle of such inkjet etching withrespect to a layer of material which may comprise an organic polymermaterial for use in an organic polymer display. However, it is to beappreciated that the principle of inkjet etching is not limited to thefabrication of such materials or such displays but may be used in anyapplication where it is necessary to define precise patterns in amaterial, such as in the fabrication of masks (for example, opticalshadow masks) or the fabrication of dewetting bank structures, also usedin the fabrication of electroluminescent displays.

As can be seen from FIG. 6A, the substrate 2 supports the layer 6 ofphotoluminescent non polar organic polymer material, which may comprisespolyfluorene or a copolymer of fluorine in combination with a conjugatedmolecule group, such as F8, F8BT or TFB or any blend thereof. The layer6 can be applied by spin coating or inkjet deposition of a solution inwhich a non-polar organic solvent, such as toluene, xylene, mesitylene,or cyclohexylebenzene, is used. A further layer 26 of a polar organicmaterial, such as poly(vinylphenol), (PVP), poly(vinylalcohol) (PVA) orpolymethylmethacrylate (PMMA), a conjugated molecule or conjugatedpolymer or a copolymer thereof, is deposited onto the photoemissivelayer 6. The layer 26 is typically about 1 micron in thickness. A polarsolvent, such as methanol, ethanol, butanol, isopropanol 1-propanol, 2-1propanol acetone or dimethylimidazolidinone, is deposited onto the layer26 from an inkjet print head 28 as a series of droplets, two of which,droplets 30 and 32, are shown in FIGS. 6A to 6F.

It has been found in the present invention that inkjet deposition ofetching substances forms a quite unique thickness profile when theetchant has dried or evaporated. There is most of the material to beetched contained in the edge region of the droplet after deposition ontoa solid surface, and there is relatively little of the material in themiddle region of the droplet. The physics of the hole formation with asolvent drop is different from that of the conventional wet etchingprocess. In the conventional case, bulky etchant and rinse liquid etchand wash away a target material. In such an etching process, thematerial is diffused into the liquid or is flowed away from thesubstrate. In the present invention, the material is not removed fromthe substrate with a bulk flow of solvent. The material is transferredlocally from the centre region of the hole to the edge. This etchingmechanism can be understood in terms of a micro-fluid-flow in a sessiledrop. This micro-fluid-flow has been proposed to explain the formationof ring-shaped “coffee stain” from a drop of solution on a solidsurface. When the drop of solution dries on the surface with a pinnedcontact line, such a flow takes place in order to compensate thedifference in the volume change and evaporation rate across the droplet.In the edge region of the drop, the evaporation rate of solvent is high,but the volume change is restricted by the pinned contact line. In thecentre region, on the other hand, a larger volume change happens with alower evaporation rate. The radial micro-fluid-flow supplies thesolution to the edge region from the centre to compensate for thisdifference. As a result, there is an enhanced deposition of the solutein the edge region and a thinner layer than expected is formed in thecentre region. The same mechanism is believed to occur in the holeformation. When a solvent drop is deposited on an insulator, theinsulator is partially dissolved in it. The insulator dissolving in thesolvent drop is carried by the flow from the centre to the edge, andsolidifies there, resulting in the formation of a crater-like hole. Thepolymer in the ridge is dissolved in deposited solvent drops, but itcannot diffuse to the centre area because the fast micro-fluid-flowpushes back the solution involving the polymer. In other words, the netmass flow of the polymer always takes place in the direction from thecentre to the edge, resulting in complete removal of the material fromthe centre region.

When the first droplet of solvent 30 is deposited onto the layer 26, thedroplet tends to spread laterally and there is partial dissolving of thelayer 26 into the solvent, as shown in FIG. 6B. As the solventevaporates, a ring 34 of the polymer material of the layer 26 builds uparound the edge of the droplet 30, as shown in FIG. 6C. This is due tothe polymer being carried by the radial micro-fluid-flow. The polymercarried is redeposited at the edge region shown in FIG. 6B. As shown inFIG. 6D the second droplet 32 of solvent is then deposited into the ring34 created by the deposition of the first droplet. From FIG. 6E, it canbe seen that the ring 34 acts to contain the second droplet 32 andprevent lateral spread of the solvent. The second droplet 32 etchesfurther into the layer 26 and as the solvent evaporates, the height ofthe ring 34 is increased, as shown in FIG. 6F. Any subsequent dropletsof solvent are likewise retained by the ring 34 until the layer 26 isetched through to expose an area 36 of the underlying materialcomprising the layer 6. Also, it should be noted that when only thefirst solvent droplet is able to dissolve the polymer right through tothe bottom of the layer and etching to the underlying material haseffectively been achieved with a single droplet, the second andsubsequent droplets are not necessarily required. The subsequentdroplets, however, after reaching the bottom of the etched hole, can beuseful to eliminate the polymer material completely from the base of thehole created. This can be particularly beneficial when the underlyingmaterial has an uneven surface, as shown in FIGS. 7A and 7B.

From FIGS. 7A and 7B it can be seen that the layer 6 has an unevensurface. When the area 36 of the layer 6 is reached by the solventdroplets, small peaks of the layer 6, shown as peaks 6 a in FIG. 7A,first become exposed. However, small areas of the layer 26, shown bydark areas 26 a in FIG. 7A, remain between the peaks 6 a of the layer 6.Because the solvent is chosen such that it will dissolve the material ofthe layer 26 but not the material of the layer 6, i.e. the material ofthe layer 6 acts as a natural etch stop for the solvent etchant, thesubsequent droplets of solvent can be used to eliminate the areas 26 afrom the area 36 without concern about etching the layer 6, to leave ahole in the layer 26 with a base, comprising the surface of the layer 6,which is not contaminated with areas of the material of the layer 26, asshown in FIG. 7B.

FIG. 8 shows measurements resulting from scanning across a nucleationring formed by inkjet deposition of, respectively, 1, 3 and 8 solventdroplets onto a relatively thick organic insulator layer, such as thelayer 26, which may comprise PVP, referred to in FIGS. 6A to 6F. What isinteresting to note from the plots shown in FIG. 8 is that as furtherdroplets of solvent are inkjet deposited onto the layer, the width ofthe hole etched into the layer tends to be better defined with wallstructures which have relatively large angles. Furthermore, the etchedhole size at a depth within the hole or ring approximately level withthe surface of the layer external to the ring tends to decrease with thedeposition of further droplets. This is due to some of the materialdissolved in the solvent in the lowermost regions of the etched holebeing re-deposited onto the wall surfaces of the hole as the solventevaporates. This is considered to be a particularly advantageous aspectof inkjet etching as very narrow and well defined patterns can be etchedin the layer to be patterned.

By utilising this aspect of inkjet etching, patterns or lines can beetched having a width less than the diameter of a droplet of the solventwhen deposited onto the layer 26. It should be noted that this aspect ofinkjet etching can be used for both solvents which dissolve the materialto be etched or substances which etch by reacting chemically with thematerial to be etched.

With current inkjet heads, droplets of solvent having a diameter ofabout 30 microns can be ejected from the nozzles of the head. However,such solvents typically have a contact angle of about 8° and thus adeposited solvent droplet typically assumes a diameter of about 60 to 70microns, once deposited onto a layer of material.

Referring to FIG. 9A, which shows a trough or channel formed in thelayer 26 by inkjet etching, the channel has a width, shown as A, whichis determined principally by the diameter of the deposited droplets ofsolvent, the type of solvent, and the wettability of the surface of thelayer 26. When subsequent droplets of solvent are selectively depositedto cover boundary portion 37 a of the channel, the material of the layer26, which forms the boundary portion 37 a, is dissolved in thesubsequent droplet of solvent. The material of the layer 26 flows withinthe droplet and concentrates towards the edge of the droplet—this is theprincipal by which the boundary portion 37 a (also known as a nucleationedge) was created during etching of the channel in the layer 26. Hence,as subsequent droplets of solvent are deposited onto the boundaryportion 37 a, the boundary portion can be caused to migrate towardsboundary portion 37 b, located on the opposite side of the channel,thereby to reduce the width A of the channel. This is shown by a shift Bin FIG. 9B. In this manner very narrow lines or channels can befabricated by etching which have a width narrower than the diameter of adeposited droplet of solvent. Furthermore, once the channel is reducedto the required width by the above technique, the process may berepeated in a position offset from the channel, for example, to theright of the subsequent droplet as shown in FIG. 9A, so as to create avery narrow ridge of the material of the layer 26 between adjacentchannels, the channels each having a width smaller than the diameter ofthe droplets of solvent as deposited onto the surface of the layer 26.

The following example explains strip-shaped cathode patterning on thephotoemissive organic layer in an organic light emitting device by wayof inkjet etching and a lift-off technique.

FIGS. 10A to 10D illustrate the patterning of a narrow line in the layer26 of organic insulator material, for example PVP, overlying the layer 6of photoemissive organic polymer supported on the substrate 2. As can beseen from FIG. 10B, the inkjet print head (not shown) is moved over thesurface of the layer 26 to deposit a plurality of droplets of thesolvent, such as methanol, ethanol, and propanol. Preferably, thedroplets are deposited so that adjacent droplets partially overlap eachother. In this manner, a narrow trough or channel is created in thelayer 26 and the process is repeated until the solvent etches completelythrough the layer 26 to expose the elongate strip area 38 of the layer6. The inkjet head is then moved laterally across the surface of thelayer 26 and the process is repeated to etch subsequent troughs in thelayer 26, adjacent troughs being separated by elongate ridges 40 of thePVP organic insulator material. The resulting structure is shown in FIG.10F. It should be noted that because the PVP organic insulator materialof the layer 26 is a polar organic material, and the photoemissiveorganic material of layer 6, such as F8, is a non-polar organicmaterial, the solvent used to dissolve and etch through the layer 26will not dissolve the layer 6. Hence, the layer 6 acts as a natural etchstop layer for the inkjet etching process. By using inkjet etching ofthe layer 26 as described above, ridges 40 having a width of less than10 microns at the base can be easily achieved.

In principle, it is possible to deposit lines of material by inkjetdeposition of a solution of the material. However, in practice it isextremely difficult to deposit material in narrow lines whose width isabout 10 microns by inkjet deposition. Even if the diameter of adeposited droplet is 10 microns, which is a very small size even for astate-of-the-art inkjet head, this 10 micron droplet spreads up to morethan 20 microns on a substrate. The resulting line width is more than 50microns from a water-based solution, which has a high surface tensionresulting in less spreading, and more than 100 microns from a non-polarorganic solvent based solution. This aspect of spreading of solution isdisadvantageous but with appropriate control of the positioning of theprint head a solution to this limitation can be provided, as has beendescribed with reference to FIGS. 9A and 9B, to enable such very narrowlines to be achieved.

Also, in some cases, there can remain a very thin PVP layer between theridges 40 on photoemissive layer 6. This thin PVP layer could lower theefficiency of light emitting devices when cathode metal is deposited onthis thin layer. However, this thin layer can be eliminated by multipledeposition of the solvent into the region between the ridges 40. Addinga small amount of a solvent of photoemissive layer 6, such as toluene orxylene, to a solvent of PVP is also very effective to remove the verythin PVP layer from the surface of the layer 6. For example, a mixtureof isopropanol 98% and toluene 2% can be used as the solvent for inkjetetching. Toluene in the mixture etches the photoemissive layer 6 veryslightly, and this promotes complete removal of the PVP layer from thesurface of photemissive layer 6.

A layer 42 of conductive material, such as a bi-layer of calcium andaluminium having a work function of less than about 4.0 electron volts,is then deposited over the ridges 40 of the PVP organic insulatormaterial. It can be seen that the inkjet etching of the layer 6 createselongate ridges 40 with steep side portions. Hence, layer 42 depositsmuch more thickly in the base areas of the troughs between the ridges 40than in regions 44 on the steep side walls of the ridges 40, as can beseen from FIG. 10G. The conductive layer 42 can be deposited using anysuitable process, such as by sputtering or evaporation deposition. Thestructure shown in FIG. 10G is then washed in a polar solvent for thePVP material of the ridges 40, such as methanol, ethanol, acetone, orpropanol. This lift-off process is possible because the layer 42 isrelatively thin or may contain small perforations in the regions 44, sothe solvent is able to reach and dissolve the ridges 40 to create anarray of conductive strips 46 overlying the photoemissive organicpolymer layer 6, as shown in FIG. 10H. The lift-off process can, ifnecessary, be performed with a sonic bath in which ultra-sonic agitationcan be applied to break down the conductive layer 42 in the regions 44and to assist the exposure of the ridges 40 to the solvent.

It will be appreciated that the conductive strips 46 can be used as acathode for the photoemissive organic polymer layer 6 and that thecathode has been fabricated, through the use of inkjet etching, withoutthe need for expensive and difficult photo masks or shadow masks. Thesolvent used in inkjet etching does not affect the surface of theemissive layer 6 because the organic material for the emissive layer 6is not soluble in the etching solvent and because it is possible toremove the patterning material (for example PVP) from the surface of theemissive layer 6 as mentioned above. Furthermore, because the ridges canbe defined to a width of less than 10 microns, there is very little lossof display area. For example, 20 microns width of spacing area betweencathode strips with 100 microns pitch for the strips can be achievedvery easily by inkjet etching and a lift-off technique and this gives anemissive area ratio of 80%, which is sufficient to provide a very brightand efficient organic light emitting display.

The principle of inkjet etching can also be used very advantageously inthe fabrication of anodes for electroluminescent displays which, asstated previously, are usually fabricated by conventionalphotolithographic techniques using photo masks, which do not lendthemselves easily to the fabrication of large area displays. Thisprocess will now be described with reference to FIGS. 11A to 11F.

In the above described example of the present invention, poly(vinylphenol)(PVP) is used as the material for patterning, but this does notmean PVP is the only material useful for inkjet etching. Inkjet etchingis available for a layer made of any soluble material or mixture ofmaterials by using solvents which have good solubility for the layer. Animportant consideration for the patterning material is to use a materialwhose solvent does not substantially dissolve and affect an underlyinglayer or substrate. With this condition, the underlying layer or thesubstrate can act as an etch stop layer, so inkjet etching can becarried out with the added advantage of not being concerned about overor under-etching. Also, not only strip shapes but also dots, or anyarbitrary pattern can be etched by control of etchant ejection andtranslation of the inkjet head.

Referring to FIG. 11A, for anode electrode fabrication the substrate 2carries a layer 48 of a non-polar organic material, such as polystyrene,polyethylene, polyisobutylene, poly(p-methyl styrene), polypropylene orF8. The substrate 2 is typically a glass substrate or a plasticssubstrate although silicon may also be used. The layer 48 can,typically, be provided by spin coating. As with the procedure describedabove for the formation of the cathode with reference to FIGS. 10A to10H, an inkjet print head is used to selectively deposit droplets of asolvent for the layer 48. From FIGS. 11A to 11C, it can be seen thatdroplets 50 of a non-polar hydrocarbon solvent, such as toluene orxylene, are deposited onto the layer 48, whereby a series of troughs areetched in the layer 48 to create ridges 52 of the non-polar materialsupported by the substrate 2. To this stage the process is the same asthat described above in relation to cathode fabrication except thatdifferent materials are used. The resulting structure can be seen inFIG. 11C. Plasma treatment with oxygen can be carried out in order tomake the surface of the substrate more wetting for polar solutions. Theinkjet print head 28 is then used to deposit droplets 54 of a conductivepolar polymer, such as Poly(3,4ethylene dioxythiophene) (PEDOT) orpolypyrrole, polyaniline, dissolved or suspended in a polar solvent,such as water. The ridges 52 are of a non-polar material so the droplets54 do not dissolve or react with the ridges but are confined within thetroughs between the ridges 52. The regions between the ridges 52 have awetting surface for a polar solvent which can be enhanced by the plasmatreatment with oxygen and, on the other hand, the non-polar ridges 52show a dewetting property with a polar solvent. When droplets of theconductive polar polymer solution are deposited onto the substrate(having a good wetting surface) between the dewetting ridges 52, thepolar solution is spontaneously confined between the ridges due to thedifference in the wetting properties between the surfaces of thesubstrate and the ridges. This self-alignment mechanism is favourable toprevent the formation of short circuits between the conducting stripseven if the width of the ridges 52 is very small, because the conductivepolar polymer is confined to the areas between the ridges and does notdeposit over the ridges.

Plasma dry etching using a vapour of fluorinated carbon such as CF4 canbe applied after inkjet etching to remove any very thin residual layerof the non-polar material from the surface of the substrate 2. Theplasma can etch the very thin residual layer. Furthermore, the surfaceof ridges 52, which is of organic material, is fluorinated by the vapourof fluorinated carbon, resulting in a very dewetting surface for polarsolution. When the substrate is of inorganic material such as glass,this surface is not fluorinated. This results in a wetting surface forthe regions between the ridges. This further enhances the self-alignmentof the conductive polar polymer between the ridges, reducing further thepossibility of short circuits between adjacent electrodes. Theself-alignment behaviour due to the difference in wettability can,therefore, be enhanced by the use of such plasma etch steps.

The polar solvent evaporates off to leave strips 56 of the conductivematerial separated by the ridges 52 of the material, as shown in FIG.11E. The structure shown in FIG. 11E can then be washed in a non-polarsolvent to dissolve the ridges 52 of non-polar material to leave theelongate strips 56 of conductive polar material on the substrate 2, asshown in FIG. 11F.

Conducting polymer material such as PEDOT, being relatively transparentand conductive, can be used to fabricate the strips 56, which maytherefore be used as an anode for a display device and, in particular,an electroluminescent display device.

As will be appreciated, the structure shown in FIG. 11F can be coatedwith a layer of photoemissive organic polymer, such as the layer 6 of F8of FIGS. 10A to 10H, followed by a layer of an inert polymer, such asPVP layer 26 of FIG. 8A. The layer 26 can then be etched using an inkjetprint head and suitable solvent as described with reference to FIGS. 10Ato 10H, to provide a cathode for the display.

It can be seen from the above description that by using an inkjet printhead very well defined patterning of the various layers can be achievedby etching with an appropriate selectively deposited solvent. Hence,such inkjet etching can be used for fabrication of the cathode electrodeor the anode electrode, or both, for a display without the use of etchmasks or shadow masks.

Dry or wet etching after inkjet etching is also useful to make patternsin a substrate or underlying layers. For example, when a structure suchas a substrate with the ridges 52 is dry-etched with oxygen plasma,troughs are formed in the substrate. By combining inkjet etching andconventional etching, it is possible to make patterns even in anon-soluble material at a low cost.

As will also be appreciated, the method of the present invention is ofparticular benefit in fabricating large area displays. As such, theinvention is not limited to etching layers supported on rigid substratessuch as glass, but may equally be used on plastics substrates.Furthermore, as an inkjet print head is used to etch the patterns in thevarious layers, the invention can be used with materials which aresupported on a web or roll of a spoolable plastics substrate. Such asubstrate can be fed from a supply spool to a take up spool past variousprocessing stations where the various layers are laid down, possibly byusing an inkjet print head, and subsequently etched, also by the use ofan inkjet print head, to provide continuous fabrication of a displaydevice on the web of material. The plastic web may then be sub-dividedto provide discrete displays.

Furthermore, it should be realised that inkjet etching is not limited todefining patterns in materials which can be dissolved in a solventdeposited by the inkjet print head. Etchants in the form of substanceswhich cause some chemical reaction with the layers to be etched can alsobe used. For example, a bi-layer of calcium and aluminium can react withsodium hydroxide. Hence, the selective deposition of sodium hydroxide byan inkjet print head onto aluminium will leave a pattern of aluminiumhydroxide on the surface, which can be washed out with water. Therefore,inkjet etching can be used for the patterning of metal layers or thefabrication of masks by appropriate selection of the substance for useas the etchant. Inkjet etched masks can be used for further dry or wetetching or chemical doping of an underlying layer. Furthermore, opticalshadow masks can also be fabricated by inkjet etching of anon-transparent soluble layer.

Additionally, it is known to use a bank structure for the fabrication oforganic polymer LED displays. Usually, the dewetting bank structure isin the form of an array of wells in the bank material which can confineeven deposited solutions from a non-polar solvent, which in general havea low contact angle and tend to spread over the surface on which theyare deposited. The bank structure can also be advantageously formed by,for example, etching a fluorinated polymer layer with inkjet depositedfluorinated organic solvents to provide the dewetting bank structure.

It has also been proposed to use hydrophilic and hydrophobic patternedsurfaces as templates for DNA or protein arrays. The hydrophilic regionsaid to contain small volumes of different DNA or protein solutionsplaced on them using an automated pin-tool loading strategy. The methodallows for efficient attachment, manipulation, and hybridisation of DNAstrands or protein on the surface of an array. However, whilst theattachment chemistry of the DNA strands or proteins to the surface isvital, the formation of the patterned substrate is also an essentialaspect to ensure that the substances under test can be precisely placedonto the array element. Typically, such array elements have beenproposed to be fabricated using photolithographic techniques. However,the patterned surface of such array elements can also be fabricatedusing the method of the present invention and, furthermore, the DNA orprotein samples under test can also be deposited onto the patternedsurface using the method of the present invention.

Whilst the present invention has been described with reference toexamples in which the material is etched through to expose areas of anunderlying material or substrate, it should also be appreciated that thepresent invention can also be employed to advantageous effect when it isrequired only to etch into and not through the material, thereby toprovide an etched pattern extending into the material. The pattern thuscreated can also then be arranged to receive a further material usingthe method of the present invention by, for example, the use of aninkjet print head.

The method of the present invention may be used to fabricate displaydevices for incorporation in many types of equipment such as mobiledisplays e.g. mobile phones, laptop personal computers, DVD players,cameras, field equipment; portable displays such as desktop computers,CCTV or photo albums; or industrial displays such as control roomequipment displays.

Several electronic apparatuses using the above described display deviceswill now be described.

<1: Mobile Computer>

An example in which a display device according to one of the aboveembodiments is applied to a mobile personal computer will now bedescribed.

FIG. 12 is an isometric view illustrating the configuration of thispersonal computer. In the drawing, the personal computer 1100 isprovided with a body 1104 including a keyboard 1102 and a display unit1106. The display unit 1106 is implemented using a display panelfabricated according to the present invention, as described above.

<2: Portable Phone>

Next, an example in which a display device is applied to a displaysection of a portable phone will be described. FIG. 13 is an isometricview illustrating the configuration of the portable phone. In thedrawing, the portable phone 1200 is provided with a plurality ofoperation keys 1202, an earpiece 1204, a mouthpiece 1206, and a displaypanel 100. This display panel 100 is implemented using a display panelfabricated according to the present invention, as described above.

<3: Digital Still Camera>

Next, a digital still camera using an OEL display device as a finderwill be described. FIG. 14 is an isometric view illustrating theconfiguration of the digital still camera and the connection to externaldevices in brief.

Typical cameras sensitize films based on optical images from objects,whereas the digital still camera 1300 generates imaging signals from theoptical image of an object by photoelectric conversion using, forexample, a charge coupled device (CCD). The digital still camera 1300 isprovided with an OEL element 100 at the back face of a case 1302 toperform display based on the imaging signals from the CCD. Thus, thedisplay panel 100 functions as a finder for displaying the object. Aphoto acceptance unit 1304 including optical lenses and the CCD isprovided at the front side (behind in the drawing) of the case 1302.

When a cameraman determines the object image displayed in the OELelement panel 100 and releases the shutter, the image signals from theCCD are transmitted and stored to memories in a circuit board 1308. Inthe digital still camera 1300, video signal output terminals 1312 andinput/output terminals 1314 for data communication are provided on aside of the case 1302. As shown in the drawing, a television monitor1430 and a personal computer 1440 are connected to the video signalterminals 1312 and the input/output terminals 1314, respectively, ifnecessary. The imaging signals stored in the memories of the circuitboard 1308 are output to the television monitor 1430 and the personalcomputer 1440, by a given operation.

Examples of electronic apparatuses, other than the personal computershown in FIG. 12, the portable phone shown in FIG. 13, and the digitalstill camera shown in FIG. 14, include OEL element television sets,view-finder-type and monitoring-type video tape recorders, carnavigation systems, pagers, electronic notebooks, portable calculators,word processors, workstations, TV telephones, point-of-sales system(POS) terminals, and devices provided with touch panels. Of course, theabove OEL device can be applied to display sections of these electronicapparatuses.

The aforegoing description has been given by way of example only and itwill be appreciated by a person skilled in the art that modificationscan be made without departing from the scope of the present invention.

1. A method of making a pattern, the method comprising: ejecting a firstdroplet from an orifice onto a first layer formed on a substrate, thefirst layer including a first material and the first droplet including afirst liquid material; forming a first trough in the first layer by thefirst droplet dissolving a portion of the first layer; ejecting a seconddroplet from an orifice onto the first trough, the second dropletincluding the first liquid material; and forming a second trough in thefirst layer by the second droplet, a diameter of the second trough beingsmaller than a diameter of the first trough.
 2. The method according toclaim 1, the diameter of the second trough being smaller than a diameterof an area covered by the first droplet when it is deposited on thefirst layer.
 3. The method according to claim 1, a first thickness ofone part of the first layer surrounding the first trough being largerthan a second thickness of parts of the first layer other than the onepart.
 4. The method according to claim 1, a diameter of the orifice fromwhich the first droplet is ejected being less than 100 microns.
 5. Themethod according to claim 1, further comprising: providing the substratewith a second layer disposed between the first layer and the substrate,the step of ejecting a first droplet including exposing a part of thesecond layer that is disposed under the first layer, the second layerbeing exposed in the first trough.
 6. The method according to claim 1,further comprising: providing the substrate with a second layer disposedbetween the first layer and the substrate, the step of ejecting a firstdroplet including exposing a part of the second layer that is disposedunder the fast layer, the second layer being exposed in the firsttrough, wherein the second layer acts as an etch stop layer.
 7. Themethod according to claim 1, the step of ejecting a first dropletincluding the liquid material dissolving the first material.
 8. Themethod according to claim 1, further comprising: forming a third layerin the second trough.
 9. The method according to claim 1, furthercomprising: providing a plurality of orifices in a nozzle, the first andsecond droplets being ejected from one or more of the plurality oforifices.
 10. The method according to claim 1, further comprising:controlling a position of the orifice from which the first droplet isejected during the ejecting of the first droplet from the orifice. 11.The method according to claim 1, the step of ejecting the first dropletfrom the orifice being performed after a position of the orifice is set.12. The method according to claim 1, further comprising: forming a thirdlayer in the second trough by depositing a third liquid material. 13.The method according to claim 1, further comprising: providing thesubstrate with a second layer disposed between the first layer and thesubstrate; forming a third layer in the second trough by depositing athird liquid material, a part of the second layer being exposed throughthe second trough, the part of the second layer having a wettability forthe third liquid material, the wettability being greater than awettability of a surface of a periphery of the second trough.
 14. Themethod according to claim 1, further comprising: providing the substratewith a second layer disposed between the first layer and the substrate;and doping a part of the second layer through the second trough, thepart of the second layer being exposed through the second trough. 15.The method according to claim 1, further comprising: forming a thirdlayer in the second trough, the third layer being a conductive layer.16. The method according to claim 1, further comprising: forming a thirdlayer in the second trough, the third layer being a conductive layerthat includes a conductive material having a work function of less than4.0 electron volts.
 17. The method according to claim 1, furthercomprising: forming a third layer in the second trough, the third layerbeing a conductive layer that comprises a conductive material includingpoly3,4-ethylene dioxythiophene.
 18. The method according to claim 1,further comprising: providing the substrate with a second layer disposedbetween the first layer and the substrate, the second layer includingpolyfluorene or a copolymer of fluorine.
 19. A method of making apattern, the method comprising: providing a first layer over asubstrate, the first layer having a first trough which is formed byejecting a plurality of first droplets by inkjet method, the first layerincluding a first material, each of the plurality of first dropletsincluding a first liquid material; ejecting a plurality of seconddroplets onto the first trough by inkjet method, each of the pluralityof second droplets including the first liquid material; and forming asecond trough in the first layer by the plurality of second droplets, adiameter of the second trough being smaller than a diameter of the firsttrough.
 20. A method of making a pattern, the method comprising:providing a first layer over a substrate, the first layer having a firsttrough which is formed by ejecting a first droplet by inkjet method, thefirst layer including a first material, the first droplet including aliquid material; ejecting a second droplet onto the first trough byinkjet method, the second droplet including the first liquid material;and forming a second trough in the first layer by the second droplet, adiameter of the second trough being smaller than a diameter of the firsttrough.